The former Toulouse, Racing-Metro and Harlequins prop claimed last week that rugby's authorities were turning a blind eye to doping in the sport.

He also suggested that doping was now as widespread in rugby as it had once been in professional cycling before the infamous Festina affair.

"Suggesting that all rugby players today are taking human growth hormone based on anatomical observations or worse, suggesting the Francois Carillo drama is related to doping, is degrading for the one who says it and unacceptable for rugby players," said Provale in a statement.

Bayonne's Carillo recently suffered a heart problem during a warm-up and has since had to end his career.

"We've been told he was unlucky and it's due to the precarious health of someone of his considerable size," fumed Benezech in an interview with Le Monde.

"I understand that 'the business must go on' but we can't say that we weren't warned."

Benezech also claimed that a simple look at the statistics related to the amount of time the ball is in play shows that players are taking something to help them.

"We went from 20 minutes of effective action to 30 minutes at the end of the 1990s which was the normal evolution due to the players becoming professionals," he said.

"But now we're explaining, even though we're already at 40 minutes, that we can hit 50 and even, why not, 60.

"That's what happened in cycling at the end of the 1990s when logic saw us lengthening the Tour de France's stages and increasing the difficulties without it posing any problems physically to the riders."

However, Provale called on Benezech to come up with proof to support his claims.

"It's up to those who accuse to prove their assertions and not for sportsmen to incessantly demonstrate their good faith in the face of rumours," added the union.

Doping in rugby has caught the public's attention recently as former France scrumhalf Jean-Pierre Elissalde claimed amphetamines were widely taken in the sport during the 1970s and 1980s.

He also admitted doping during his career.

Just a few days before that, high-ranking French anti-doping official Francoise Lasne claimed rugby had returned the highest proportion of positive dope tests in France in 2012.